Wave reduction gears are used in rotating table devices in gear-cutting machines and a variety of other machine tools. This wave reduction gear has a small number of components, and can carry out positioning with a high degree of precision. One known type of wave reduction gear is a cup-type wave reduction gear comprising an annular rigid internally toothed gear, a cup-shaped flexible externally toothed gear disposed therein, and a wave generator fitted inside the externally toothed gear. The cup-shaped flexible external gear has a cylindrical trunk portion, a diaphragm and boss for sealing off one end of the cylindrical trunk portion, and external teeth formed in a portion of an external peripheral surface of the other open end of the cylindrical trunk portion. The wave generator is fitted in an open end portion of the cylindrical trunk portion where the external teeth are formed on an outer peripheral surface thereof.
A wave reduction gear provided with lubricating mechanism is disclosed in Patent Documents 1 through 3.    [Patent Document 1] Japanese Laid-open Patent Application No. 09-250610    [Patent Document 2] Japanese Laid-open Patent Application No. 09-250609    [Patent Document 3] Japanese Laid-open Patent Application No. 09-250611
Oil bath lubrication is generally used in a case where a wave reduction gear having this structure is used in high-speed rotation. In this case, problems arise in that the motor load increases due to the viscosity resistance of the lubricating oil. Another problem known as lubrication oil suction occurs when the wave generator is rotated at high speeds by the motor, causing negative pressure inside the flexible externally toothed gear. Lubricating oil is thereby suctioned into the externally toothed gear, and an adequate amount of lubricating oil is not supplied to the bearing components of the wave generator.